Anti-knock gasoline manufacture



April 1960 L. s. GALSTAUN ETAL 2,932,612

ANTI-KNOCK GASOLINE MANUFACTURE Filed March 21, 1956 LOW OOTANE NAPHTHA CHARGE 4 REFORM/N6 ZONE 6- FRAOT/ONAT/ON ZONE HEAVY STREAM 9 /0 OFF -11 6A5 HEART AUXILIARY FRAOT/ON- AT/O/V J T HYDROGA REG/V5 /8 a BOTTOMS l4 I5 T0 OTHER USES E X 7" RAO T/ON F) ZONE RAFFl/VA TE EXTRA 0r BL E NO/NG' ZONE INVENTORS L/one/ 5. Gals tau/1 A/VT/- KNOCK Lou/'5 0. Romp/n0 GA SOL NE Will/aim A. Vanaenburg ANTLKNQQK GASOLINE MANUFACTURE Lionel S. Galstaun, Oakland, and Louis D. Rampino and William A. Vandenburg, Concord, Califi, assignors to Tide Water Oil Company, a corporation of Delaware Application March 21, 1956, Serial No. 572,893

7 Claims. (Q1. 203-%) This invention relates to the catalytic reforming of naphtha fractions to produce gasoline constituents of high anti-knock quality. More particularly, it relates to a combination of catalytic reforming and separation processes whereby a greater yield of high quality product is obtained than can be achieved by catalytic reforming alone. Still more particularly, it relates to an improved method for obtaining aromatic and other anti-knock hydrocarbons from catalytic reformates for the manufacture of high-octane motor fuel.

Progress in the automotive industry has resulted in the development of gasoline engines of higher and higher compression pressures, requiring gasoline fuels with correspondingly higher anti-knock properties or octane rating. To meet this demand, the petroleum industry has developed various processes for producing gasoline of increased octane rating. One of the more efficient of such processes is catalytic reforming, wherein low-octane naphtha is contacted under pressure in the vaponphase with suitable catalyst at temperatures above 800 F., in the presence of substantial volumes of hydrogen. A common type of catalyst used for catalytic reforming is platinum supported on a carrier of alumina and/or silica. Several such platinum catalysts are marketed which will produce good yields of 85 to 90 research octane number (ASTM Method D 908-53) reformate under operating conditions sufiiciently mild that the catalyst can be used for extended periods of time without regeneration to remove carbon formed by undesirable reactions.

More recent developments in the automotive industry have created a need for gasoline having a research octane I number substantially above 90 (before the addition of tetraethyl lead or other anti-knock compound) and preferably above 96. T meet this requirement by catalytic reforming processes now in use, it has been necessary to increase the severity of operating conditions to an extent that a substantial amount of hydro-cracking occurs with concomitant decrease in naphtha yield, increased equipment and operating cost to regenerate the catalyst (by burning off the carbon formed), and increased cost for a suitable catalyst capable of tolerating frequent regeneration Without a prohibitive amount of deterioration.

In the present invention, certain new separation processes are combined with catalytic reforming to produce a higher yield of usable components for a 96 to 98 (or higher) octane gasoline that can be produced by catalytic reforming alone under conditions severe enough to produce the same anti-knock quality.

Heretofore, a large yield of high-octane blending components has been obtained by solvent-extracting the reformate (i.e., the liquid components emerging from the catalytic reformer) with a suitable extracting agent 2,932,612 Patented Apr. 12, 1960 ice to obtain a solvent extract of high aromatic content and then recycling the raffinate to the reforming step. In this prior-art process, the high-octane extract is, without further treatment, blended into the motor gasoline. An object of the present invention is to improve this prior art process markedly, so as to overcome a number of disadvantages inherent therein.

We have discovered that greatly improved efficiency can be obtained by subjecting only a middle fraction of the reformate to the extraction step and by using the light and heavy fractions (with or without further fractionation) directly in the gasoline. As a result of our new process, there is substantial saving in the cost of extraction and the size of the extraction equipment, a reduction of gums and other catalyst-inactivating agents in the reforming stage, and an improved finished gasoline blend.

We have found that the distribution of hydrocarbons in catalytic reformate conforms to the following pattern:

1) There is a light portion distilling up to about P. which contains only a small amount of aromatic hydrocarbons. It is predominate in paraflins, including isoparamns, having reasonably high octane rating and excellent lead-susceptibility. The parafiins in this portion, however, are only with great difficulty improved by further reforming.

(2) A middle, or heart-cut, portion distilling between about 160 F. and about 330 F. contains large quantities of aromatic hydrocarbons in admixture with similar amounts of paraflins having very low octane rating.

(3) A third portion distilling above about 330 F, is very highly aromatic and has inherently a high octane number in the. region of 96 and above without tetraethyl lead. The aromatics contained in this portion are less readily separated from parafiins by extraction with solvents.

(4) There is usually a portion boiling above about 400 F. which is almost entirely aromatic. However, this portion generally contains substantial amounts of dicyclic aromatics such as naphthalene, the two methyl naphthalenm and the several dimethyl naphthalenes. We have found that the presence of these dicyclic aromatics in gasoline, even in low percentages (such as 1% or even less), is deleterious and causes varnishes, gums and lacquers in engines using such fuel. The aromatics contained in this fraction are likewise relatively diflicult to separate from paraflins by solvent extraction.

Broadly, our invention contemplates fractionaliy distilling a catalytic reformate to isolate into separate frac tions at least the first three, and preferably the four. portions described above. Fractions 1 and 3 are blended directly into gasoline. Fraction 2 is solvent refined, or otherwise treated, to extract therefrom the aromatic hydrocarbons, which are blended into gasoline. The rafiinate from the extraction is again catalytically reformed, advantageously in the same reformer, to produce additional reformate. By these processing steps, the aromatics and the high-octane paraffins in reformate can be recovered for use in gasoline and substantially all the lower octane paraflins can be reformed to extinction, with a minimum of size, investment cost and operating expense of the solvent extraction plant. The extraction operation is most efficient, and the aromatic content of stocks charged to catalytic reforming is reduced to a minimum thereby enhancing the reforming operations When, as is preferred, fraction number 4 is separated and rejected, the objectionable dicyclic aromatics in normal reformates are eliminated from the finished gasoline.

Summarizing, the invention comprises catalytically reforming a naphtha, fractionating the reformate, extracting aromatics from a heart-cut thereof, and recharging the rafiinate from the extraction to the reformer. This rafiinate is substantially less in quantity than that usually obtained by solvent refining the whole liquid reformate, it is clean and contains substantially all the reformable paraflinic compounds that can be separated by extraction. In a preferred form of the invention, theheavy fraction obtained by fractionating the reformate is itself refractionated to produce an overhead product of high aromatic content having a very high octane rating, and to reject a small amount of bottoms that tends to be harmful to engines. The overhead product from the refractionation of the heavy fraction '(or the entire heavy fraction where the bottoms components are not objectionable) is blended with the highly aromatic extract from the heart-cut. To this blend may be added the light fratcion of the reformate in any amount required to meet volatility and octane requirements. If desired, the light fraction may be refractionated and selected components thereof may be used in the finished gasoline blend, as the desired volatility and other characteristics of the blend demand.

Separation of the aromatics from the heart-cut may be by any suitable process, such as for example, by use of silica gel; by extractive distillation in the presence of phenol, cresylic acids, sulfolanes or glycol-Water mix tures; or by solvent extraction (eg with liquid sulfur dioxide or diethylene glycol). The low anti-knock naphtha fed to the process may be a virgin naphtha or it may be a fraction produced from other refining processes such as hydrodesulfurization.

The invention may be more readily understood by reference to the drawing which is a diagrammatic flow diagram of the process. Naphtha in line 1, together with raftinate in line 2 and recycle hydrogen in line 3, is charged to catalytic reforming zone 4, wherein the mixture of hydrocarbons and hydrogen is passed at elevated pressure in the vapor phase through a bed of reforming catalyst at temperatures in excess of 800 F., and under suitable conditions of time and hydrogen concentration, to convert a substantial amount of the paraffinic charge to aromatic hydrocarbons with concomitant isomerization of some paraflinic constituents and production of hydrogen and certain low-boiling hydrocarbons. As is well known to the art, increased time and temperature and reduced pressures in catalytic reforming tend to increase cracking reactions with resulting formation of larger quantities of normally gaseous hydrocarbons and carbon. Preferably, the conditions in zone 4 are maintained sutficiently moderate to permit treatment of at least 30 barrels of naphtha per pound of catalyst. While such conditions Vary with the naphtha treated and with the particular catalyst used, those conversant with catalytic reform ing can readily select suitable conditions.

The efiluent from the catalytic reforming zone 4, comprising hydrogen, normally gaseous hydrocarbons and normally liquid aromatic and parafiinic hydrocarbons, is discharged through line 5 into a main fractionating zone 6 which includes suitable traps, stills, absorption equipment and the like to fractionate the efliuent into (1) a hydrogen fraction containing upwards of about 70% hydrogen, shown as leaving zone 6 through line 7; (2) a gas fraction composed principally of the C to C hydrocarbons formed in zone 4, but which may also contain some hydrogen and any excess C hydrocarbons not usable in the finished gasoline, shown as leaving through line 8; (3) a light hydrocarbon fraction leaving through line 9; (4) a heart cut or middle hydrocarbon fraction, leaving through line 10, and (5) a heavy hydrocarbon fraction leaving through line 11.

Part of the hydrogen fraction in line 7 is recycled to the reforming zone 4 through line 3 to maintain the required ratio of hydrogen to hydrocarbon therein, in accordance with known principles. If desired, such hydrogen fraction may be treated to remove hydrogen sultide or other unwanted impurities prior to entry into zone 4. The remainder of the hydrogen fraction in line 7 is passed through line 12 for any desired disposal. Likewise, the gas fraction in line 8 is disposed of as desired.

The light hydrocarbon fraction in line 9, may comprise approximately 25 of the total which leaves through lines 9, 10 and 11 and will be, generally speaking, those hydrocarbons which boil in the range between butane and about 160 F. and which contain less than about 20% aromatics. This fraction is not a useful source of aromatics upon further reforming and, due to the nature of catalytic reforming, contains high percentages of isoparaflins of good anti-knock value. These may be passed directly to blending zone 13 to be included in the finished gasoline or, optionally, part or all may be sent through line 14 to be used for other purpose.

The heart-cut, leaving the main fractionation zone 6 through line 10, may constitute approximately 50% of the total hydrocarbons leaving through lines 9, 10 and 11, being more or less dependent upon the composition of the crude naphtha and the desired characteristics of the finished blend. Normally, it includes an aromatic content that varies from about 10% to 20% in its lower boiling constituents to about 70% to 80% in its higher boiling constituents. It is substantially free from dicyclic aromatic compounds and other gum-forming substances. Its constituents will lie, generally speaking, within a distillation range from about 160 F. to about 330 F.

The medium-boiling hydrocarbons in line 10 are charged to an extraction zone 15. In the extraction zone 15, the hydrocarbons are separated into an extract (composed predominately of aromatic hydrocarbons, shown as leaving through line 16) and rafiinate (composed predominately of paraffinic hydrocarbons, shown as leaving through line 2). As indicated prior, any one of the various well-known methods for separating aromatic from parafinic hydrocarbons may be used for the separation in extraction zone 15. Extraction with diethylene glycol has proved suitable, and will be used elsewhere herein for illustration, though liquid sulfur dioxide and other extracting agents may also be used.

The extract in line 16 is passed to the blending zone 13 where it may be blended with the light hydrocarbons from line 9. The rafiinate is returned through line 2 to the reforming zone 4 for further treatment. It is thus seen that the raffinate is treated to extinction, with the products of the process being a predominately aromatic gasoline and gas.

The heavy hydrocarbons which leave the main fractionation zone 6 through line 11 may comprise approximately 25% of the total hydrocarbons leaving through lines 9, 10 and 11. This heavy fraction is highly aromatic normally having 70% to aromatic content or even more and having a very high octane number. However,

this heavy hydrocarbon fraction also may contain naphthalene, alpha methyl naphthalene, beta methyl naphthalene and other dicyclic aromatics, which are undesirable either as gasoline components or as feed to the reformer and are preferably eliminated from both the raflinate and the blended gasoline. Hence, the heavy fraction may be passed from line 11 to a second fractionating zone 17 to remove therefrom a bottoms fraction indicated as being withdrawn through line 18. Generally speaking, the bottoms are those hydrocarbons which boil above 400 F. and may have a volume of about 1% to 5% of the liquid components leaving reforming zone 4. For a particular naphtha charge the proportions may differ, and what is desired is to exclude substantially all the dicyclic aromatics from both the gasoline and the raffinate and to recover them in the bottoms, while recovering substantially all the valuable mono-cyclic aromatics in the gasoline. The predominate, overhead portion of the heavy hydrocarbons emerges through line 19 as highoctane, high-aromatics-content components that are passed to the blending zone 13.

Thus, the high-octane gasoline leaving blending zone 13 through line contains a mixture of the high-octane clean components of the heavy hydrocarbons, line 19, and the predominately aromatic extract from the heartcut hydrocarbons, line 16. As desired, part or all of the light hydrocarbons, line 9, or ingredients from other sources may be added in zone 13 for augmenting the quantity, correcting the volatility, or further improving the octane number.

To further illustrate the invention, the following examples of operations under typical conditions are presented.

EXAMPLE 1 About 7,300 barrels per day of a mixture of approximately 60% straight run naphtha and 40% thermally cracked naphtha, after catalytic hydrodesulfurization, is charged to a catalytic reformer together with about 2,700 barrels per day of raflinate obtained from a later stage of the process.

The naphtha mixture before hydrodesulfurization may have an ASTM distillation range of l70410 F. After hydrodesulfurization, the distillation range may be 130- 424 F. This stock is prefractionated to give a reformer charge having a distillation range of 160 to 400 F. After reforming, the resultingdepropanized reformate may have a distillation range of 90 F. to 425 F.

The catalytic reforming is conducted with a typical platinum reforming catalyst under mild conditions. The hydrogen needed to maintain the desired hydrogen-tohydrocarbon ratio during the reforming is obtained by recycling part of the hydrogen produced during the re forming reactions. The efi luent' from the reformer is cooled and passed to a high pressure gas separator from which a hydrogen stream of about 88% purity is wit drawn Part of this stream supplies the recycled hydrogen, and the remainder (representing the main part of the hydrogen produced by reforming) is diverted to other uses.

The liquid hydrocarbons from the high pressure separator are stabilized at lower pressure to produce a gas stream composed of propane and lighter hydrocarbons, a stream containing the C C and C hydrocarbons, a clehexanized heart-cut stream containing about 45% aromatic hydrocarbons and a stream containing heavy hydrocarbons boiling above about 330 F. The heart-cut is extracted by counter-current extraction with liquid sulfur dioxide at F. to give about 2700 barrels per day of recycle rafiinate containing about 5% aromatics and an extract stream of about 2740 barrels per day of dehexanized, highly aromatic blending stock (containing about 75% aromatics) having a clear research octane number of 99.7 suitable for use as a major constituent of high anti-knock gasoline :or for other blending purposes as desired. Table I shows additional data relating to this example.

Reformer charge:

Fresh naphtha, bbls./day Recycle rafiinate, bbls./day

Total, bb1s./day 10,000

6 Reformer yields:

Hydrogen fraction (net), M c.f./day 4,000 Dry gas fraction, M c.f./day 8,200 0.; to C bbls./day 2,090 Dehexanized reformate, bbls./day 5,440 Extraction Conditions:

Volume S0 per volume reformate 1.25 Temperature, F. 25 Extraction yields:

Raflinate, bbls./day 2,700 Extract, bbls./day 2,740

Percent Overall Processing Yields of Fresh BbL/Day Feed Light Fraction-G4, G5, 06 28.6 2, 090 Heart-Out Extract 37. 5 2, 740 Heavy Overhead Fraction 21.0 1, 530 Yield of Blending Components 87.1 0, 360

The total reformate (lines 9, 10 and 11 in the drawing) before extraction may have an analysis such as the typical one shown in Table II.

Table II.-Analysls of reformate cuts Research Octane Vol. N o. Aro- Dist. Cut No. percent matics, ASTM Range,

of Volume Gum F. Charge Clear +3.0 cc. percent TEL/gal.

100 84. 6 95. 0 46. 0 1. 8 85-425 1 13.0 79. 8 94. 5 2.0 0. 0 -146 10.0 66. 0 86. 5 7.0 0. 0 152-234 10.0 71.0 89.1 27.0 0. 0 198-235 10. 0 65. 1 85. 4 29.0 0. 0 222-269 10. 0 83. l 94. 8 44. 0 0. 0 254-313 10. 0 87. 3 95. 5 53.0 0. 0 284-328 10.0 90.9 97. 6 57. 0 0. 0 294-332 10.0 97. 2 99. 8 69. 0 0. 0 319-339 9 l0. 0 99.0 101. 6 78.0 0. 0 343-369 10 Btms 7.0 104. 6 95.0 369-440!- 1 Including 3.0% distillation loss.

it will be noted that the first portion of the reformate up to approximately 25% has a low aromatic content, i.e., less than 20%; the last 25% has a high aromatic content, i.e., more than 70%. The middle 50% portion has an average of about 50% aromatics. It will also be noted that the ASTM gum of all the overhead cuts was nil.

The bottom cut was further fractionated into 1% (of original charge) cuts with results shown in Table III.

Table III.-ASTM gum and dicyclic aromatic content of heavy fractions of reformate 1 Guts 3A through 6A are expressed as equivalent to isooctane plus the indicated amounts of tetraethyl lead.

Table III shows that the very heavy fractions of ref ormate all have high ASTM gum; the bottom 1% cut, which contained 64% dicyclic aromatics, showed 15.1% naphthalene and 45.4% alpha methyl naphthalene.

The relative tendency of reformate distillates to form gum is shown in Table IV. A

7 Table IV.AST M gum of reformate distillates of a'ifierent percents overhead Research Octane No. ASTM ASTM Percent Bottoms removed Dist. Gum

13. Clear +3.0 cc.

TEL/gal.

121-364 Nil 80. 5 93. 2 122-374 1 81. 2 93. 126386 1 82. 2 94. 0 125-396 1. 4 83. 0 94. 5 125-411 83. 0 94. 5

The data in Table IV show that a reformate distillate corresponding to approximately 99% overhead would generally have satisfactory quality.

Where the light fraction is sent to the blending zone 13 through line 9, the composition of the fuel of this example may be as shown in Table V.

Table V.Composition of blend from light, medium and Where the light fraction is withdrawn through line 14, the blend shown in Table V1 is characteristic.

Table VI.-C0mposition of blend from medium and heavy fractions Research Octane No. Percent Boiling of Total Range, F.

Clear +3.0 cc.

TEL/gal.

Extract from Medium Fraction 64. 2 160-330 09. 7 102. 5 Overhead from Heavy Fraction 35. 8 330-410 99. 7 102. 3 Total Blend 100 160-410 09. 7 102. 4

This is a very high octane fuel, and marks a significant advance over the prior art.

EXAMPLE 2 To illustrate the comparative yields and quality of product when solvent extracting a 160 to 330 F. heartcut of reformate in accordance with the invention and when solvent extracting a whole reformate according to conventional practice, the following data are presented from pilot plant tests. A reformate similar to that described in Example 1 was depentanized and extracted with diethylene glycol in a twenty stage counter-current Scheibel type pilot extractor. A 160 to 330 F. heartcut (57.8%) of the same reformate was extracted in a separate test under comparable conditions. Data for the two operations are given in Table VII.

It will be noted that solvent treatment of the depentanized reformate yielded 46% of 99 octane gasoline, whereas the combination of heart-cut extract and heavy reformate provided 58% of equal quality gasoline blending stock.

This was accomplished while solvent treating only a heart-cut amounting to 57.8% of the depentanized reformate; and furthermore, the solvent to feed ratio required for treating the heart-cut was only 3.5 as compared to 5.5 for the whole depentanized reformate.

The savings in operating costs and in capital investment in solvent treating facilities are readily apparent. The cost of installing and operating the fractionating tower are minor in comparison to the comparable costs for solvent treatment.

Table VII Depentan- 160-330 ized Refor- Heart-cut mate Extraction Conditions:

Volume DEG/volume Reformate 5. 5 3. 5 Temperature, F 875 375 Water content of DEG, percent 2 2 Pressure, p.s.i.g 150 150 Number of Stages (actual)- 20 20 10 Feed Rate, (XL/min 20 25 Reflux, percent of feed-.. 17 Aromatics in feed, percen 48 42 Extraction Yields:

Rafiinate, percent of ieed 54 51.5 Extract, percent of feed 46 48. 5 Aromatics in Extract, perccut 73 68 Aromatics in Rafiinate, percent 21 15 Overall YieldsBasis, 10,000 cc. of Depentanized Reform-ate:

Light; Fraction Not used 7 Heart-cut Extract 2, 800 Heavy Fraction 3,000 Depentanized Reformate Extract 4, 600

Research Octane No., clear 99 99 Research Octane No., +3 ml. TEL 103 103 The following engine tests illustrate the effect of removal of heavy ends of reformate on engine cleanliness. The test procedure involved a 40-hour engine run on a dynamometer under conditions chosen to correlate, on an accelerated scale, with field performance. In this test a 216.5 cubic-inch, six-cylinder Chevrolet engine was run continuously for forty hours at a speed of 1900 rpm. (plus or minus 25 rpm.) under an engine load of 36 B.H.P. (plus or minus 1 B.H.P.). The jacket coolant inlet temperature was kept at 155 F. minimum, the jacket coolant outlet temperature was kept within two degrees of 170 F., and the crankcase oil temperature was kept within two degrees of 190 F. The air-fuel ratio was 14.5 (plus or minus 0.5) to 1. The spark advance was 35 (plus or minus 3). The spark plug gap, ignition cam angle, valve clearnnce, exhaust back pressure and other similar conditions were also maintained at predetermined values. Before the first test and between tests the engine was disassembled and cleaned, and a new set of piston rings was installed. The engine was given a standard two-hour break-in before the actual test was begun.

After each test run of forty hours, the engine was dismantled and inspected, and was rated on ten items, as follows:

(1) Piston skirt varnish rating.

(2) Cylinder wall varnish rating.

(3) Intake valve stem deposit rating.

(4) Intake valve tulip deposit rating.

(5) Intake port deposit rating.

(6) Overall engine sludge rating.

(7) Overall engine varnish rating.

On these first seven items, the rating runs between 0 for dirty to 10 for clean.

(8) Corrosion or rust rating (10 for none, 9 for light, 8 for medium, and 7 for heavy corrosion).

(9) Stuck ring rating (10, minus 0.5 demerit for each 90 of ring stuck in the groove).

(10) Tight ring rating (10, minus 0.5 demerit for each tight ring).

A perfectly clean engine will thus rate 100. A total 0 rating of 85 is considered acceptable if the piston skirt varnish is 7.5 or better. The test results are shown below:

Efject of fractionating reformate on engine cleanliness To those skilled in the art, various changes and modifications of the invention may suggest themselves without departing from the spirit and scope of the invention. As stated prior, various alternates for solvent extraction are known, such as extractive distillation and selective adsorption. Part, or all, of the raflinate may be diverted from line 2 and used for other purposes, if desired, while retaining many of the advantages of the invention. Likewise, though the optirnum cut-points for recovery of the intermediate fraction may be 160 F. and 330 F., as stated hereinbefore, substantial advantages from the invention would still be obtained even by a considerable variation from these figures.

We claim:

1. A process for producing highly aromatic anti-knock gasoline components which comprises: catalytically reforming, in the presence of hydrogen and at elevated temperatures, a naphtha fraction within the gasoline boiling range to convert a substantial portion of said fraction to aromatic hydrocarbons with the production of additional hydrogen, normally gaseous hydrocarbons and a liquid reformate having a boiling range extending from the normally gaseous hydrocarbons to above 400 F separating the resulting reformate into (1) a fraction having a boiling range below about 160 F. and containing less than about 20% aromatics; (2) a heart-cut middle fraction with a boiling range of about 160 to 330 F.; and (3) a heavy fraction having a boiling range above about 330 F. and containing more than about 70% aromatics; separating said middle fraction into a predominately aromatic portion and a predominately paraffinic portion; returning said predominately paraffinic portion to the reforming step; additionally fractionating said heavy fraction to recover an overhead substantially free of dicyclic aromatics and about 1% to 5% of bottoms hoiling over 400 F. and containing substantially all the dicyclic aromatics of said reformate; and blending said predominately aromatic portion of said middle fraction and the overhead portion of said heavy fraction into gasoline.

2. A process for producing highly aromatic anti-knock gasoline components, which comprises: catalytically reforming, in the presence of hydrogen and at elevated temperatures, a naptha fraction within the gasoline boiling range and having some components with boiling points above 330 F, to convert a substantial proportion of said fraction to aromatic hydrocarbons with the production of additional hydrogen, the reformed product having a distillation range extending above 330 F.; separating the resultant reformate into a low-boiling fraction consisting essentially of components boiling below 160 F, a relatively high-boiling fraction consisting essentially of components boiling above 330 F., and an intermediate fraction with a boiling range of about 160 F. to 330 F.; further separating said intermediate fraction into a predominantly aromatic portion and a predominantly parafiinic portion; returning said predominantly parafiinic portion to the reforming step; and blending said predominantly aromatic portion into gasoline.

3. The process of claim 2 in which at least a major portion of the high-boiling fraction is also blended into the gasoline.

4. A process for producing highly aromatic anti-knock gasoline components which comprises: catalytically reforming, in the presence of hydrogen and at elevated temperatures, a naphtha fraction having some components boiling above 330 F., to convert a substantial portion of said fraction to aromatic hydrocarbons with the production of additional hydrogen, the resulting reformate also having some components boiling above 330 F.

and containing a detrimental amount of dicyclic aromatics boiling above 400 F.; separating the resultant reformate into a relatively low-boiling fraction boiling below 160 F., a relatively high-boiling fraction boiling above 330 F., and an intermediate fraction boiling from about 160 F. to about 330 F.; separating said intermediate fraction into a predominantly aromatic portion and a predominantly paraffinic portion; returning said predominantly paraflinic portion to the reforming step; distilling said high-boiling fraction to remove as overhead constituents having a distillation range of about 330 F. to 400 F., and to leave a bottoms portion of about 1 to 5% by volume of the reformate and having a boiling point over 400 F., and blending said predominantly aromatic portion of said intermediate fraction and said overhead.

5. A process for producing highly aromatic anti-knock gasoline components which comprises: catalytically reforming, in the presence of hydrogen and at elevated temperatures, a naphtha fraction including some components boiling above about 330 F, to convert a substantial portion of said fraction to aromatic hydrocarbons with the production of additional hydrogen and some deleterious dicyclic aromatics; separating the resultant reformate into (1) a low-boiling fraction whose components boil below 160 F. and which contain relatively small proportions of aromatics and a major proportion of hydrocarbons substantially incapable of producing aromatics by further reforming; (2) a heart-cut middle fraction with a boiling range of about l60330 F.; and (3) a heavy fraction Whose components boil above 330 F.; separating said middle fraction into a predominantly aromatic portion and a predominantly paraflinic portion; returning said predominantly parafiinic portion to the reforming step; distilling said heavy fraction to remove a small bottoms portion between 1% and 5% of the volume of the liquid reformate and boiling above 400 F. and containing substantially all the dicyclic aromatics of said reformate; and blending together at least said predominantly aromatic portion of said middle fraction and the overhead obtained from distilling said heavy fraction.

6. In a catalytic reforming process for producing antiknock gasoline components wherein a catalytic reformate having a boiling range from about F. to above 400 F. is solvent extracted into an aromatic extract and a paraffinic raffinate and the resulting rafiinate is recycled to the reforming process, the improvement comprising subjecting to the extracting step only a -330 F. heart-cut of said reformate, to obtain a ratfinate for the recycle step substantially free of dicyclic aromatics and of parafiinic hydrocarbons boiling below about 160 F.

7. In a catalytic reforming process for producing antiknock gasoline components wherein a catalytic reformate having components boiling above 330 F. is fractionated to provide a portion boiling below about 330 F. and a portion boiling above 330 F., the improvement comprising further distilling the higher boiling portion to distill therefrom an overhead product leaving a bottoms product boiling above 400 F. and containing not over 5% by volume of said reformate and including substantially all the dicyclic aromatics of said reformate, and

blending said overhead in gasoline.

References Cited in the file of this patent UNITED STATES PATENTS 2,304,183 Layng et al. Dec. 8, 1942 2,363,263 Rosen Nov. 21, 1944 2,409,695 Laughlin Oct. 22, 1946 2,626,893 Morrow Jan. 27, 1953 2,651,597 Corner et al. Sept. 8, 1953 2,697,684 Hemminger et al Dec. 21, 1954 

1. A PROCESS FOR PRODUCING HIGHLY AROMATIC ANTI-KNOCK GASOLINE COMPONENTS WHICH COMPRISES: CATALYTICALLY REFORMING, IN THE PRESENCE OF HYDROGEN AND AT ELEVATED TEMPERATURES, A NAPHTHA FRACTION WITHIN THE GASOLINE BOILING RANGE TO CONVERT A SUBSTANTIAL PORTION OF SAID FRACTION TO AROMATIC HYDROCARBONS WITH THE PRODUCTION OF ADDITIONAL HYDROGEN, NORMALLY GASEOUS HYDROCARBONS AND A LIQUID REFORMATE HAVING A BOILING RANGE EXTENDING FROM THE NORMALLY GASEOUS HYDROCARBONS TO ABOVE 400* F., SEPARATING THE RESULTING REFORMATE INTO (1) A FRACTION HAVING A BOILING RANGE BELOW ABOUT 160*F. AND CONTAINING LESS THAN ABOUT 20% AROMATICS, (2) A HEART-CUT MIDDLE FRACTION WITH A BOILING RANGE OF ABOUT 160* TO 330*F., AND (3) A HEAVY FRACTION HAVING A BOILING RANGE ABOVE ABOUT 330*F. AND CONTAINING MORE THAN ABOUT 70% AROMATICS, SEPARATING SAID MIDDLE FRACTION INTO A PREDOMINATELY AROMATIC PORTION AND A PREDOMINATELY PARAFFINIC PORTION, RETURNING SAID PREDOMINATELY PARAFFINIC PORTION TO THE REFORMING STEP, ADDITIONALLY FRACTIONATING SAID HEAVY FRACTION TO RECOVER AN OVERHEAD SUBSTANTIALLY FREE OF DICYCLIC AROMATICS AND ABOUT 1% TO 5% OF BOTTOMS BOILING OVER 400*F. AND CONTAINING SUBSTANTIALLY ALL THE DICYCLIC AROMATICS OF SAID REFORMATE, AND BLENDING SAID PREDOMINATELY AROMATIC PORTION OF SAID MIDDLE FRACTION AND THE OVERHEAD PORTION OF SAID HEAVY FRACTION INTO GASOLINE. 